If you like to jailbreak and unlock your iPhone, you’ll want to backup your existing SHSH blobs before you install a new version of iOS. With the release of iOS 4.2 just around the corner, it’s a good idea to do this now if you intend on unlocking your device in the future.

How to save/backup SHSH blobs with Firmware Umbrella

This process is detailed for the Mac but it’s very similar for Windows users:

This will save your SHSH blob to your local disk as well as Cydia where it can be accessed and restored from later

That’s really all there is to it, the new version of TinyUmbrella makes this process easier than it was in the past since you no longer have to manually edit /etc/hosts yourself.

What are SHSH blobs and why do I need them?

SHSH stands for Signature Hash, SHSH blobs are basically secure signature hash files that are unique to your device thanks to it’s ECID (Exclusive Chip ID). You’ll want to backup your SHSH blobs because Apple only allows you to restore to firmware that has a signed SHSH, and this signature only lasts for a limited time. Once this digital signature ends, you can no longer restore to that firmware (ie: downgrade iOS and firmware). This is very important for jailbreakers and those who unlock the iPhone in particular, because certain jailbreak and unlock exploits are only valid on older versions of firmware.

iOS Device Firmware & Download Links

If you need them, here are comprehensive lists of iOS device firmware and IPSW file downloads: